1. Field
The present disclosure relates generally to generating images, and in particular, to generating images using synthetic apertures. Still more particularly, the present disclosure relates to a method and apparatus for increasing a synthetic aperture baseline to improve the angular resolution of an image using photons having a non-classical state.
2. Background
Aperture synthesis, a form of interferometry, may include mixing light received through a collection of apertures to produce images that have a same angular resolution as an aperture having the size of the entire collection of apertures. In this manner, the collection of apertures forms a “synthetic aperture”. As used herein, the “angular resolution” of an image is the minimum angular distance relative to the synthetic aperture between objects in the image at which those objects can be resolved, or distinguished. The angular resolution of an image may be expressed in radians, degrees, arcminutes, arcseconds, or some other unit of angular measurement.
The angular resolution of an image generated using a synthetic aperture may be determined by the baseline of the synthetic aperture. As used herein, the “baseline” of a synthetic aperture is the maximum physical separation between the apertures that make up the synthetic aperture along a line normal to the direction of the object relative to the synthetic aperture. Increasing the baseline may increase the angular resolution.
With some currently available synthetic apertures, photons received through, for example, a pair of apertures in the synthetic aperture may be transported to a same location and physically interfered with each other. The maximum baseline for these types of synthetic apertures may be limited by the potential for the loss of photons and/or phase information along the transmission lines used to transport the photons. These transmission lines may take the form of, but are not limited to, optical fibers, vacuum pipes, and/or other types of transmission lines.
With these types of transmission lines, as the distance that the photons need to travel increases, the potential for the loss of photons and/or phase information also increases. Consequently, the limits to the maximum baseline that can be achieved may limit the angular resolution that can be achieved. For example, some currently available synthetic aperture systems may be unable to produce images having an angular resolution of less than about one nanoradian.
In some cases, the baseline for a synthetic aperture may be increased using quantum teleportation. In particular, quantum teleportation may be used to transfer the state of first photons received through a first aperture to second photons received through a second aperture without physically transporting the first photons to the second photons. Quantum teleportation may be performed using entangled photons from a local source.
Quantum teleportation may allow longer baselines to be achieved when compared to physically interfering the photons received through apertures with each other. However, the maximum baseline that can be achieved may still be constrained by the limited number of entangled photons that can be emitted from the local source during a given time interval.
Further, fluctuations in the number of entangled photons that may be emitted during a given point in time may require more measurements than desired to be generated to produce an image. Additionally, these fluctuations may increase the minimum brightness of an object that can be imaged more than desired. Therefore, it would be desirable to have a method and apparatus that takes into account at least some of the issues discussed above, as well as other possible issues.